Styryl dyes

ABSTRACT

The present invention provides styryl dyes which have absorption maxima at a wavelength of 400 nm or less and are sensitive to a laser beam with a wavelength of 450 nm or less, light absorbents and optical recording media which comprise the styryl dyes, and a process for producing the styryl dyes which comprises reacting with an aldehyde compound a quaternary ammonium salt of nitrogen atom containing heterocyclic compound having an active methyl or active methylene group.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of Ser. No.09/890,711, filed Aug. 9, 2001, the entire contents of which is herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to organic dye compounds, and moreparticularly, to styryl dyes which have absorption maxima at awavelength of 400 nm or less.

BACKGROUND OF THE INVENTION

In a multimedia age, optical recording media such as CD-R (a write-oncememory using compact disc) and DVD-R (a write-once memory using digitalvideo disc) are now of great importance. Most of the conventionaloptical recording media can be roughly classified into inorganic opticalrecording media which have recording layers composed of inorganicsubstances such as tellurium, selenium, rhodium, carbon, or carbonsulfide; and organic optical recording media which have recording layersmainly composed of light absorbents containing organic dye compounds.

Among these optical recording media, organic optical recording media canbe usually prepared by dissolving a polymethine dye in an organicsolvent such as 2,2,3,3-tetrafluoro-1-propanol (abbreviated as “TFP”hereinafter), spin coating the solution onto the surface of apolycarbonate substrate, drying the solution to form a recording layer,and sequentially forming and coating onto the surface of the recordinglayer a reflection layer comprising a metal such as gold, silver orcopper, and a protection layer comprising an ultraviolet ray hardeningresin. When compared with inorganic optical recording media, organicones may have the drawback that their recording layers are susceptibleto change under environmental lights such as reading and natural light.Organic optical recording media, however, have the advantage that theycan be made into optical recording media at a lesser cost because theirrecording layers can be directly formed by coating light absorbents insolution on the surface of substrates. Further, organic opticalrecording media composed of organic materials are now mainly used aslow-cost optical recording media because they are substantially free ofcorrosion even when contacted by moisture or sea water and becauseinformation recorded therein in a prescribed format can be read out byusing commercially available read-only readers after establishingthermal-deformation-type optical recording media, a kind of organicoptical recording media.

What is urgently required in organic optical recording media is toincrease their storage capacity to suit to this multimedia age. Theresearch for such an increment, which is now being eagerly continued inthis field, is to increase the recording capacity per one side from 4.7GB (giga bite) to 15 GB or more by shortening the wavelength for writinginformation to 450 nm or less from the wavelengths of 635-650 nm whichare commonly used. The high-density optical recording media have thecapacity to record movie and animations for six hours in picture qualityof standard television or for two hours even in relatively-high picturequality of high definition television. However, since most organic dyecompounds now used in the conventional optical recording media can notbe used with visible light with a wavelength of 450 nm or less, theycould not fulfill the need for high-storage density required in manyfields.

In view of the foregoing, the object of the present invention is toprovide organic dye compounds which have absorption maxima at awavelength of 400 nm or less and substantially absorb a visible lightwith a wavelength of 450 nm or less when formed in a thin layer, and toprovide uses thereof.

SUMMARY OF THE INVENTION

The present inventors eagerly studied and screened compounds. As aresult, they found that specific styryl dyes (may be called “styryldyes” hereinafter), which are obtainable through a step of reacting aquaternary ammonium salt of nitrogen heterocyclic compound having anactive methyl- or active methylene-group with an aldehyde compound, haveabsorption maxima at a wavelength of 400 nm or less and substantiallyabsorb visible light with a wavelength around 400 nm. The presentinventors confirmed that the styryl dyes, which substantially absorbvisible light with a wavelength of 450 nm or less when formed in a thinlayer, form remarkably minute pits at a relatively high density inoptical recording media by irradiating with a laser beam with awavelength of 450 nm or less. The present invention was made based onthe creation of novel styryl dyes and the discovery of theirindustrially useful characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the visible absorption spectra of one of the styryl dyes ofthe present invention when in a solution form and in a thin layer form,respectively.

FIG. 2 is the visible absorption spectra of another styryl dye of thepresent invention when in a solution form and in a thin layer form,respectively.

FIG. 3 is the visible absorption spectra of a conventional relatedcompound when in a solution form and in a thin layer form, respectively.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to the styryl dyes represented by Formula1.Formula 1:

In Formula 1, R₁ represents a hydrogen atom, an aliphatic hydrocarbongroup, ether group, acyl group, halogen, or cyano group. The aliphatichydrocarbon group in R₁ represented that having up to six carbon atoms,usually, from one to five carbon atoms such as methyl, ethyl, propyl,isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl,neopentyl, or tert-pentyl group. Examples of the ether groups aremethoxy, ethoxy, propoxy, isopropoxy, butoxy, tert-butoxy, pentoxy, andphenoxy groups. Examples of the acyl groups are formyl, acetyl,propionyl, butyryl, tert-butyryl, benzoyl, o-tolyl, m-tolyl, and p-tolylgroups. Examples of the halogens are fluorine, chlorine, bromine, andiodine. One or more of the hydrogens in the aliphatic hydrocarbon group,ethergroup, and acyl group may be replaced with a short-chain aliphatichydrocarbon group such as methyl, ethyl, or propyl group; a short-chainether group such as methoxy, ethoxy, or propoxy group; or a halogen suchas fluorine, chlorine, bromine, or iodine.

In Formula 1, φ₁ represents a heterocycle which is represented by anyone of Formulae 2 to 8.

Throughout Formulae 2 to 7, A represents a monocyclic- orpolycyclic-aromatic-ring or heterocycle. Examples of the aromatic ringare benzene and naphthalene rings. Examples of the heterocycle arepyridine, quinoline, and quinoxaline rings. The aromatic ring andheterocycle may have one or more substituents, for example, a halogenatom such as fluorine, chlorine, bromine, or iodine atom; a short-chainaliphatic hydrocarbon group such as methyl, trifluoromethyl, ethyl,propyl, isopropyl, butyl, isobutyl, sec-butyl, or tert-butyl group; ashort-chain ether group such as methoxy, trifluoromethoxy, ethoxy,propoxy, isopropoxy, butoxy, or tert-butoxy group; an alkylaminosulfonylgroup such as methylaminosulfonyl, dimethylaminosulfonyl,ethylaminosulfonyl, diethylaminosulfonyl, propylaminosulfonyl,dipropylaminosulfonyl, butylaminosulfonyl, or dibutylaminosulfonylgroup; an aromatic hydrocarbon group such as phenyl, biphenylyl,o-tolyl, m-tolyl, p-tolyl, xylyl, mesityl, o-cumenyl, m-cumenyl,p-cumenyl, or naphthyl group; an ester group such as methoxycarbonyl,trifluoromethoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, acetoxy,trifluoroacetoxy, or benzoyloxy group; nitro group, cyano group, carboxygroup, or sulfo group. When A is not present in Formulae 2 to 7, one ormore substituents similar to those that are similar to A may be in theposition where A is located.

Throughout Formulae 2 to 8, R₂ represents an aliphatic hydrocarbon groupselected from those having up to eight carbon atoms, usually, up to sixcarbon atoms such as methyl, ethyl, propyl, isopropyl, isopropenyl,1-propenyl, 2-propenyl, 2-propynyl, butyl, isobutyl, sec-butyl,tert-butyl, 2-butenyl, 2-butynyl, 1,3-butadienyl, pentyl, isopentyl,neopentyl, 1-methylpentyl, 2-methylpentyl, 2-pentenyl, 2-pentynyl,2-penten-4-ynyl, hexyl, or isohexyl group. The aliphatic hydrocarbongroup may have one or more substituents, for example, a halogen such asfluorine, chlorine, bromine, or iodine; an ether group such as methoxy,trifluoromethoxy, ethoxy, propoxy, isopropoxy, butoxy, tert-butoxy,benzyloxy, or phenoxy group; an ester group such as methoxycarbonyl,trifluoromethoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, acetoxy,trifluoroacetoxy, or benzoyloxy group; a carboxy group; a sulfo group; ahydroxy group; an amido group such as acetylamino or benzoylamino group;an aromatic hydrocarbon group such as phenyl, biphenylyl, o-tolyl,m-tolyl, p-tolyl, xylyl, mesityl, o-cumenyl, m-cumenyl, p-cumenyl, ornaphthyl group; or heterocyclic group such as 2-pyridyl, 2-quinolyl,2-tetrahydropyranyl, 2,2-dimethyl-1,3-dioxolane-4-yl,1,3-dioxolane-2-yl, 3,5-dimethylisooxazole-4-yl, 3-piperidinyl,piperidino, morpholino, 1-piperazinyl, pyrrolidine-1-yl,1-methyl-2-pyrrolidinyl, 2-benzoimidazolyl, 5-uracil, orbenzotriazole-1-yl group.

In Formula 4, R₃ represents a hydrogen atom or an aliphatic hydrocarbongroup which is identical to or different from R₂. Representativeexamples of the aliphatic hydrocarbon group are short-chain groups suchas methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, ortert-butyl group, which may have one or more substituents, for example,an ether group such as methoxy, trifluoromethoxy, ethoxy, propoxy,isopropoxy, butoxy, or tert-butoxy group; an ester group such asmethoxycarbonyl, trifluoromethoxycarbonyl, ethoxycarbonyl,propoxycarbonyl, acetoxy, trifluoroacetoxy, or benzoyloxy group; or anaromatic hydrocarbon group such as phenyl, o-tolyl, m-tolyl, p-tolyl,xylyl, mesityl, o-cumenyl, m-cumenyl, p-cumenyl, or nitrophenyl group.

Furthermore, in Formula 1, φ₂ represents a monocyclic/orpolycyclic/aromatic ring or heterocycle which may include one or morenitrogen atoms in the ring, for example, a benzene, pyridine,pyrimidine, pyridazine, naphthalene, quinoline, or quinoxaline ring. Thearomatic ring and heterocycle may have one or more substituents. Thesubstituents are selected from those having up to eight carbon atoms,usually, one to six carbon atoms, for example, an aliphatic hydrocarbongroup such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl,sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl,1-methylpentyl, 2-methylpentyl, hexyl, or isohexyl group; a short-chainether group such as methoxy, trifluoromethoxy, ethoxy, propoxy,isopropoxy, butoxy, or tert-butoxy group; an amido group such asacetylamino or benzoylamino group; a halogen such as fluorine, chlorine,bromine, or iodine; and cyano group, nitro group, hydroxy group, sulfogroup, or carboxy group. When φ₂ is a nitrogen-atom-containingheterocycle, the nitrogen atom may combine with a similar aliphatichydrocarbon group as in R₂ in φ₁ to form an ammonium salt. When φ₂ hastwo hydroxy groups as a substituent and the hydroxy groups combine withadjacent carbon atoms in φ₂, the hydroxy groups may react with an oxocompound such as formalin to form a cyclic structure such as a dioxolering.

X⁻ in Formula 1 represents an arbitrary counter ion and is usuallyselected from inorganic acid ions such as fluoride, chloride, bromide,iodide, perchrolide acid, periodic acid, phosphoric acid hexafluoride,antimony hexafluoride, tin acid hexafluoride, phosphoric acid,fluoroboric acid, and tetrafluoroboric acid ions; organic acid ions suchas thiocyanic acid, benzensulfonic acid, naphthalenesulfonic acid,naphthalenedisulfonic acid, p-toluenesulfonic acid, alkylsulfonic acid,benzenecarboxylic acid, alkylcarboxylic acid, trihaloalkylcarboxylicacid, alkylsulfonic acid, trihaloalkylsulfonic acid, nicotinic acid, andtetracyanoquinonedimethane ions; and organic metal complex ions such asazo, bisphenyldithiol, thiocatechol chelate, thiobisphenolate chelate,and bisdiol-α-diketone. “n” is the number of X⁻ to balance the electriccharge in the styryl dyes, and is usually an integer selected from oneand two.

The present invention relates to styryl dyes having the structures asmentioned above, particularly, to those which have absorption maxima ata wavelength of 400 nm or less, and desirably those which substantiallyabsorb a visible light with a wavelength of 450 nm or less when formedin a thin layer. Concrete examples of the styryl dyes are thoserepresented by Chemical Formulae 1 to 60. Since all of them haveabsorption maxima at a wavelength of 400 nm or less and substantiallyabsorb a visible light with a wavelength around 400 nm, they havediversified uses in the fields which need organic compounds that absorbthe aforesaid visible light. Among the styryl dyes, those, whichsubstantially absorb a visible light with a wavelength of 450 nm or lesswhen formed in a thin layer, particularly, absorb the visible light inthe absorption end of longer wavelength region of the absorptionmaximum, are remarkably useful as a material for producing a recordinglayer of high density optical recording media such as DVD-Rs for thecoming generation.

The styryl dyes of the present invention can be prepared by variousprocedures. They can be preferably and economically produced by a stepof reacting a quaternary ammonium salt of nitrogen atom containingheterocyclic compound having either an active methyl- or activemethylene-group with an aldehyde compound. With this method, the styryldyes of the present invention can be produced in a desired yield byreacting a compound represented by Formula 9 having φ₁ and R₁corresponding to those in Formula 1 with a compound represented byFormula 10 having φ₂ corresponding to those in Formula 1.

For example, appropriate amounts (usually about equal mols) of compoundsrepresented by Formulae 9 and 10 are placed in a reaction vessel, andthe resulting mixture is dissolved in an adequate solvent, if necessary,and then reacted at ambient temperature or under heating and stirringconditions, for example, a reflux in the presence of an appropriateamount of a basic compound such as sodium hydroxide, potassiumhydroxide, sodium carbonate, potassium carbonate, sodiumhydrogencarbonate, potassium hydrogencarbonate, ammonia, triethylamine,piperidine, pyridine, pyrrolidine, aniline, N,N-dimethylaniline,N,N-diethylaniline, or N-methyl-2-pyrrolidone; an acidic compound suchas hydrochloric acid, sulfuric acid, nitric acid, methanesulforic acid,p-toluenesulfonic acid, acetic acid, acetic anhydride, propionicanhydride, trifluoroacetic acid, or trifluorosulfonic acid; or a Lewisacidic compound such as aluminium chloride, zinc chloride, tintetrachloride, or titanium tetrachloride.

As to solvents which can be used in the present invention, for example,hydrocarbons such as pentane, hexane, cyclohexane, octane, benzene,toluene, and xylene; halides such as carbon tetrachloride, chloroform,1,2-dichloroethane, 1,2-dibromoethane, trichloroethylene,tetrachloroethylene, chlorobenzene, bromobenzene, and α-dichlorobenzene;alcohols and phenols such as methanol, ethanol, 1-propanol, 2-propanol,1-butanol, 2-butanol, isobutyl alcohol, isopentyl alcohol, cyclohexanol,ethylene glycol, propylene glycol, 2-methoxyethanol, 2-ethoxyethanol,phenol, benzyl alcohol, cresol, diethyleneglycol, triethylene glycol,and glycerin; ethers such as diethyl ether, diisopropyl ether,tetrahydrofuran, tetrahydropyran, 1,4-dioxane, anisole,1,2-dimethoxyethane, diethylene glycol dimethyl ether,dicyclohexyl-18-crown-6, methylcarbitol, and ethylcarbitol; ketones suchas furfural, acetone, ethyl methyl ketone, and cyclohexanone; acids andacidic derivatives such as acetic acid, acetic anhydride,trichloroacetic acid, trifluoroacetic acid, propionic anhydride, ethylacetate, butyl carbonate, ethylene carbonate, propylene carbonate,formamide, N-methylformamide, N,N-dimethylformamide, N-methylacetamide,N,N-dimethylacetamide, hexamethylphosphoric triamide, and phosphorictrimethyl; nitriles such as acetonitrile, propionitrile, succinonitrile,and benzonitrile; nitro compounds such as nitromethane and nitrobenzene;sulfur-containing compounds such as dimethylsulfoxide and sulfolane; andwater can be used and arbitrarily used in a combination, if necessary.

In general, when solvents are used, the greater the volume of solventsthe lower the reaction efficiency. On the contrary, the lower the volumeof solvents the more difficult homogeneous heating and stirring of thecontents becomes and undesirable side reactions may easily occur. Thus,the volume of solvents is desirably set to a level up to 100-folds,usually, in the range of 5-50-folds to the total volume of materialcompounds by weight. The reaction is complete within 10 hours, usually,0.5-10 hours, depending on the kinds of reactants and the reactionconditions. The reaction progress can be monitored by conventionalmethods, for example, thin layer chromatography, gas chromatography, andhigh-performance liquid chromatography. After completion of thereaction, the styryl dyes of the present invention with desired counterions are obtainable by subjecting the reaction mixture to a conventionalcounter ion-exchange reaction, if necessary. Thus, all of the styryldyes represented by Chemical Formulae 1 to 60 are obtainable in adesired yield by the above method. Compounds represented by Formulae 9and 10 are obtainable in accordance with conventional methods to form acyclic nucleus in the styryl dyes.

The styryl dyes thus obtained can be used in the form of a reactionmixture without any further treatment, but are usually used after beingpurified by conventional techniques which are generally used forpurifying their related compounds, such as dissolution, extraction,separation, decantation, filtration, concentration, thin layerchromatography, column chromatography, gas chromatography,high-performance liquid chromatography, distillation, crystallization,and sublimation. If necessary, these methods can be used in combination.When the styryl dyes of the present invention are used in dye lasers andoptical recording media such as DVD-Rs, it is preferable that the styryldyes of the present invention be distilled, crystallized, and/orsublimated prior to use.

The light absorbents of the present invention comprise one or more ofthe styryl dyes and include those which utilize the nature of the styryldyes which substantially absorb visible light with a wavelength around400 nm. The compositions or the physical forms of the light absorbentsare not restricted. Therefore, the light absorbents of the presentinvention may comprise one or more other compounds in addition to thestyryl dyes, depending on use. One of the fields in which the lightabsorbents of the present invention can be advantageously used isoptical recording media. In this field, the light absorbents of thepresent invention are suitable as a material for producing recordinglayers of optical recording media using a laser beam with a wavelengthof 450 nm or less as a writing light. In using the light absorbents ofthe present invention in optical recording media, unless the usedeviates from the object of the present invention, the styryl dyes canbe mixed with other light absorbents comprising other organic dyecompounds which are sensitive to visible light and one or moreconventional materials used in optical recording media, such as alight-resistant improver, binder, dispersing agent, flame retardant,lubricant, antistatic agent, surfactant, thermal interference inhibitor,plasticizer, color fixing agent, developer, and dissolving assistant, ifnecessary.

Explaining the uses of the light absorbents of the present invention byexamplifying organic optical recording media (organicheat-deformative-type optical recording media), the optical recordingmedia of the present invention can be prepared in accordance withconventional organic recording media because the styryl dyes of thepresent invention require no special treatment beyond the treatmentswhich are commonly used in this art. For example, one or more of thestyryl dyes of the present invention can be mixed with one or more otherorganic dye compounds which are sensitive to visible light, and one ormore conventional light-resistant improvers, binders, dispersing agents,flame retardants, lubricants, antistatic agents, surfactants, thermalinterference inhibitors, and plasticizers to control the reflection rateand the light absorption rate in a recording layer, if necessary. Theresulting mixture is dissolved in an organic solvent, and the solutionis uniformly coated over either surface of the substrates by means ofspraying, soaking, roller coating, or rotatory coating methods; anddried to form a recording layer, a thin layer comprising lightabsorbents, and if necessary, followed by forming a reflection layer tobe closely attached onto the recording layer by the method of vacuumdeposition, chemical vapor deposition, sputtering, or ion plating usingmetals such as gold, silver, copper, platinum, aluminium, cobalt, tin,nickel, iron, and chromium or using conventional organic materials forreflection layers to impart a reflection efficiency with which thewritten information can be read, for example, 20% or more, andpreferably 30% or more. Then ultraviolet-ray-hardening resins orthermosetting resins, which contain flame retardants, stabilizers,and/or antistatic agents are spin coated over the recording layer, andthen the coated are hardened resins by either irradiating light orheating to form a protection layer to be closely attached onto thereflection layer to protect the recording layer from scratches, dusts,spills, etc. Thereafter, if necessary, a pair of the above substrateswith recording, reflection, and recording layers are faced and attachedtogether using, for example, adhesives or viscous sheets; or protectionplates, which are comprising the same materials and shapes as thesubstrates, are attached to the protection layers of the substrates.

As another organic dye compounds usable in combination with the styryldyes of the present invention, dye compounds are particularly restrictedas long as they are sensitive to visible light and can modulate thelight reflection- and the light absorption-rates of recording layers ofoptical recording media. As the organic dye compounds, the followingcompounds can be used in an arbitrary combination, if necessary:Acridine dye, azaannulene dye, azo dye, azo metal complex dye,anthraquinone dye, indigo dye, indanthrene dye, oxazine dye, xanthenedye, dioxazine dye, thiazine dye, thioindigo dye, tetrapyrapolphyradinedye, triphenylmethine dye, triphenylthiazine dye, naphthoquinone dye,pyrromethene dye, phthalocyanine dye, benzoquinone dye, benzopyrandye,benzofuranone dye, polyphyrin dye, rhodamine dye, and polymethine dyessuch as cyanine dye, merocyanine dye, oxonol dye, azulenium dye,squalilium dye, styryl dye, pyririum dye, thiopyririum dye, andphenanthrene dye in which the same or different rings are bound to bothends of polymethine chain such as monomethine, dimethine, trimethine,tetramethine, pentamethine, hexamethine, or heptamethine. The chain andrings can have one or more substituents. Examples of the ring areimidazoline ring, imidazole ring, banzoimidazole ring, α-naphthimidazolering, β-naphthimidazole ring, indole ring, isoindole ring, indoleninering, isoindolenine ring, benzoindolenine ring, pyridinoindolenine ring,oxazoline ring, oxazole ring, isooxazole ring, benzooxazole ring,pyridinooxazole ring, α-naphthoxazole ring, β-naphthoxazole ring,selenazoline ring, selenazole ring, benzoselenazole ring,α-naphthselenazole ring, β-naphthselenazole ring, thiazoline ring,thiazole ring, isothiazole ring, benzothiazole ring, α-naphththiazolering, β-naphththiazole ring, tellurazoline ring, tellurazole ring,benzotellurazole ring, α-naphthtellurazole ring, β-naphthtellurazolering, acridine ring, anthracene ring, isoquinoline ring, isopyrrolering, imidanoxaline ring, indandione ring, indazole ring, indaline ring,oxadiazole ring, carbazole ring, xanthene ring, quinazoline ring,quinoxaline ring, quinoline ring, chroman ring, cyclohexanedione ring,cyclopentandione ring, cinnoline ring, thiodiazole ring, thiooxazolidonering, thiophene ring, thionaphthene ring, thiobarbituric acid ring,thiohydantoin ring, tetrazole ring, triazine ring, naphthalene ring,naphthyridine ring, piperazine ring, pyrazine ring, pyrazole ring,pyrazoline ring, pyrazolidine ring, pyrazolone ring, pyran ring,pyridine ring, pyridazine ring, pyrimidine ring, pyrylium ring,pyrrolidine ring, pyrroline ring, pyrrole ring, phenazine ring,phenanthridine ring, phenanthrene ring, phenanthroline ring, phthalazinering, pteridine ring, furazane ring, furan ring, purine ring, benzenering, benzoxazine ring, benzopyran ring, morpholine ring, and rhodaninering. As the organic dye compounds used in combination with the styryldyes of the present invention, they desirably have an absorption maximain the visible region, particularly, at wavelengths of 400-850 nm, whenformed in a thin layer.

The light-resistant improvers are, for example, nitroso compounds suchas nitrosodiphenylamine, nitrosoaniline, nitrosophenol, andnitrosonaphthol; and metal complexes such as dithiolate metal complexes,for example, “NKX-1199”(bis[2′-chloro-3-methoxy-4-(2-methoxyethoxy)dithiobenzyl]nickel)produced by Hayashibara Biochemical Laboratories, Inc., Okayama, Japan,and formazane metal complexes, which all can be arbitrarily used incombination, if necessary. Preferable light-resistance improvers arethose which contain metal complexes, and the most preferable ones aremetal complexes, more preferably, formazane compounds which have apyridine-ring at C-5 and a pyridine or furan ring at C-3 of formazaneskeleton as disclosed in Japanese Patent Application No. 163,036/99,titled “Formazane metal complexes”, and complexes with metals such asnickel, zinc, cobalt, iron, copper, and palladium, which have thetautomer of the aforesaid compounds as a ligand. In the case of usingsuch a light-resistance improver in combination, the styryl dyes of thepresent invention can be effectively prevented from undesirabledeterioration, fading, color changing, and quality changing, which areinducible by environmental lights such reading- and natural-lights,without lowering the solubility of the light absorbents of the presentinvention in organic solvents and substantially deteriorating preferableoptical features. As to a composition ratio, 0.01-5 moles of alight-resistance improver(s), desirably, 0.1-1 moles, can beincorporated into one mole of the styryl dye(s) while increasing ordecreasing the ratio. The light-resistant improver(s) are notnecessarily other compound(s) which exist separately from the styryldyes of the present invention, and if necessary, they can be formulatedinto salts, complexes, or compounds by combining the styryl dyes withorganic metal complex anions, which are capable of improving the lightresistance as disclosed in Japanese Patent Kokai Nos. 19,355/89,139,043/93, 323,478/97, and 6,651/98. These include conventionalcompounds such as azo, bisphenyldithiol, phenyldithiol,thiocatecholchelate, thiobisphenolatechelate, or bisdithiol-α-diketoneby using appropriate spacers and crosslinking agents such as alkoxidesor cyanates of titanium, zirconium, aluminium, etc., or complexes ofthese metal elements having carbonyl compounds or hydroxy compounds asligands.

The styryl dyes of the present invention have satisfactorily-highsolubility in organic solvents without substantially causing undesirableproblems in actual use, and do not particularly restrict the types oforganic solvents used for coating the light absorbents of the presentinvention over substrates. Thus, in the preparation of optical recordingmedia according to the present invention, arbitrary organic solvents canbe selected from the following conventional ones which are arbitrarilyused in combination, if necessary: TFP frequently used to prepareoptical recording media and the following organic solvents other thanTFP: For example, hydrocarbons such as benzene, toluene, and xylene;halides such as carbon tetrachloride, chloroform, 1,2-dichloroethane,1,2-dibromoethane, trichloroethylene, tetrachloroethylene,chlorobenzene, bromobenzene, and α-dichlorobenzene; alcohols and phenolssuch as methanol, ethanol, propanol, isopropanol,2,2,2-trifluoroethanol, butanol, isobutanol, isopentanol, cyclohexanol,ethylene glycol, propylene glycol, 2-methoxyethanol (methyl cellosolve),2-ethoxyethanol (ethyl cellosolve), phenol, benzyl alcohol, cresol,diethylene glycol, triethyleneglycol, glycerine, and diacetone alcohol;ethers such as diethyl ether, diisopropyl ether, tetrahydrofuran,tetrahydropyran, 1,4-dioxane, anisole, 1,2-dimethoxyethane,dicyclohexyl-18-crown-6, methylcarbitol, and ethylcarbitol; ketones suchas furfural, acetone, 1,3-diacetylacetone, ethyl methyl ketone, andcyclohexanone; esters such as ethyl acetate, butyl acetate, ethylenecarbonate, propylene carbonate, and trimethyl phosphate; amides such asformamide, N-methylformamide, N,N-dimethylformamide, andhexamethylphosphoric triamide; nitriles such as acetonitrile,propionitrile, and succinonitrile; nitro compounds such as nitromethaneand nitrobenzene; amines such as ethylene diamine, pyridine, piperidine,morpholine, and N-methylpyrrolidone; and sulfur-containing compoundssuch as dimethylsulfoxide and sulfolane.

Particularly, since the styryl dyes of the present invention haverelatively high solubilities in easily volatile organic solvents such asTFP, methyl cellosolve, ethyl cellosolve, and diacetone alcohol, theyare substantially free from dye crystallization when they aresequentially dissolved in the organic solvents, coated on substrates,and dried and do not cause inconsistent thickness and surface of theformed recording layers. Most of the styryl dyes of the presentinvention exert desirable solubilities in non-halogen solvents, forexample, cellosolves such as methyl cellosolve and ethyl cellosolve,alcohols such as diacetone alcohol, and ketones such as ethyl methylketon and cyclohexanone. When the styryl dyes of the present inventiondissolve in the non-halogen solvents and the obtained solutions arecoated over the plastic substrates, the solvents neither damage thesubstrates nor pollute the environment, which is an advantage.

Conventional substrates can be used in the present invention and areusually processed with suitable materials, for example, into discs, 12cm in diameter and 0.1-1.2 mm in thickness, to be conformed to final useby methods such as compression molding, injection molding,compression-injection molding, photopolymerization method (2P method),thermosetting integral method, and light setting integral method. Thesediscs can be used singularly or plurally after they have beenappropriately attached together with adhesive sheets or adhesive agents,etc. In principal, any materials for substrates can be used in thepresent invention as long as they are substantially transparent and havelight transmissivity of at least 80%, and preferably 90% or more atwavelengths ranging from 350 nm to 800 nm. Examples of such materialsare glasses, ceramics, and others such as plastics includingpolyacrylate, polymethyl methacrylate, polycarbonate, polystyrene(styrene copolymer), polymethylpentene, polyester, polyolefin,polyimide, polyetherimide, polysulfone, polyethersulfone, polyarylate,polycarbonate/polystyrene alloy, polyestercarbonate,polyphthalatecarbonate, polycarbonateacrylate, non-crystallinepolyolefin, methacrylate copolymer, diallylcarbonatediethylene-glycol,epoxy resin, and phenol resin, where polycarbonate and acrylate are mostfrequently used. In plastic substrates, concaves for expression ofsynchronizing signals and addresses of tracks and sectors are usuallytransferred to the internal circle of the tracks during their formation.The present invention does not restrict the form of concaves and theconcaves are preferably formed to give 0.3-0.8 μm in average wide and50-150 nm in depth.

The styryl dyes of the present invention can be prepared into 0.5-5%(w/w) solutions of the organic solvents as mentioned above whileconsidering the viscosity of the solutions, and then uniformly coatedover a substrate to form a recording layer of 10-1,000 nm, preferably,50-300 nm in thickness. Prior to the coating, a preliminary layer can beformed over the substrate to improve the protection and the adhesionability of the substrate, if necessary. Materials of the preliminarylayer are, for example, high-molecular substances such as ionomerresins, polyamide resins, vinyl resins, natural resins, silicon, andliquid rubbers. In the case of using binders, the following polymers canbe used alone or in combination in a weight ratio of 0.01-10 times ofthe light absorbent(s): Cellulose esters such as nitrocellulose,cellulose phosphate, cellulose sulfate, cellulose acetate, cellulosepropionate, cellulose lactate, cellulose palmitate, and celluloseacetate/propionate; cellulose ethers such as methyl cellulose, ethylcellulose, propyl cellulose, and butyl cellulose; vinyl resins such aspolystyrene, poly(vinyl chloride), poly(vinyl acetate), poly(vinylacetal), poly(vinyl butyral), poly(vinyl formal), poly(vinyl alcohol),and poly(vinyl pyrrolidone); copolymer resins such as styrene-butadienecopolymers, styrene-acrylonitrile copolymers,styrene-butadiene-acrylonitrile copolymers, vinyl chloride-vinyl acetatecopolymers, and maleic anhydride copolymers; acrylic resins such aspoly(methyl methacrylate), poly(methyl acrylate), polyacrylate,polymethacrylate, polyacrylamide, and polyacrylonitrile; polyesters suchas poly(ethylene terephthalate); and polyolefins such as polyethylene,chlorinated polyethylene, and polypropylene.

Explaining the manner for using the optical recording media according tothe present invention, the high-density optical recording media of thepresent invention such as DVD-Rs can write information at a relativelyhigh density by using a laser beam with a wavelength of 450 nm or less,more particularly, a laser beam with a wavelength around 350-450 nmirradiated by semiconductor laser elements such as InN, GaN, InGaN,InAlGaN, InGaNAs, BInN, InGaNP, InP, GaP, GaAsP, and SiC, whichoscillate in the blue color or violet color region; or a distributedfeedback-type laser, which oscillates in the red color region, and towhich set a second harmonics generating mechanism to a semiconductorelement of AlGaAs. To read recorded information, laser beams are usedwith wavelengths identical to or slightly longer or shorter than thoseused for writing information. As for the laser power for writing andreading information, in the optical recording media of the presentinvention. It is preferably set to a relatively high level, whichexceeds the threshold of the energy required for forming pits, inwriting information. It is preferably set to a relatively low level,i.e., a level of below the threshold when used in reading recordedinformation, although the power levels can be varied depending on thetypes and ratios of the light-resistant improvers used in combinationwith the light absorbents of the present invention and further thewriting speed. Generally, the levels can be controlled to outputs ofover 5 mW for writing, usually in the range of 10-50 mW, and to outputsof 5 mW or lower for reading, usually in the range of 0.1-5 mW. Therecorded information is read by detecting the changes of both thereflection light level and the transmission light level in the pits andthe pit-less part on the surface of optical recording media by the lightpick-up manner.

Accordingly, in the optical recording media of the present invention,remarkably minute pits with a pit width of below 0.4 μm/pit and a trackpitch of below 0.74 μm used in the conventional DVD-R, can be formed ata relatively high density by using a laser beam with an oscillatingwavelength of 450 nm. For example, in using a substrate, 12 cm indiameter, it can realize an extremely high density optical recordingmedium with an optical recording capacity far exceeding 4.7 GB (gigabytes) per one side, i.e., that of about two hours of information ofsound and images in relatively high image quality of high definitiontelevision which could hardly be attained in the commonly used DVD-Rs.

Since the optical recording media of the present invention can recordinformation including characters, images, and sound at a relatively highdensity, they are advantageously useful as recording media forprofessional and family uses to record and care for documents, data, andcomputer software. Particular examples of the types of industries andthe forms of information to which the optical recording media can beapplied are drawings of construction and engineering works, maps,ledgers of roads and rivers, aperture cards, architectural sketches,documents of disaster protection, wiring diagrams, arrangement plans,information from newspapers and magazines, local information, andconstruction specifications, which all relate to construction andengineering works; blueprints, ingredient tables, prescriptions, productspecifications, product price tables, parts lists, information formaintenance, case study files of accidents and problems, manuals forclaims, production schemes, technical documents, sketches, details,company's house-made product files, technical reports, and analysisreports, which are all used in production; customers information,information of business connections, information of companies,contracts, information of newspapers and magazines, business reports,company's credit research, and stock lists, which are all used in sales;information of companies, records of stock prices, statisticaldocuments, information from newspapers and magazines, contracts,customer lists, documents of application, notification, licenses,authorization, and business reports, which are all used in finance;information regarding real property and transportation, sketches ofconstruction, maps, local information, information from newspapers andmagazines, contracts for lease, information about companies, stocklists, traffic information, and information regarding businessconnections, which are all used in real property and transportation;diagrams of writings and pipe arrangements for electric and gassupplies, documents of disaster protection, tables of operation manuals,documents of investigations, and technical reports; medical charts,files of clinical histories and case studies, and diagrams for medicalcare institution relationships; texts, collections of questions,educational documents, and statistical information; scientific papers,records in academic societies, monthly reports of research, researchdata, documentary records and indexes thereof, which are all used inuniversities, colleges, and research institutes; inspection data,literatures, patent publications, weather maps, analytical records ofdata, and customer files, which are all used for information; casestudies on laws; membership lists, history notes, records of works,products, competition data, data of meetings and congresses, which areall used in several organizations/associations; sightseeing information,traffic information, and local information, which are all used forsightseeing; indexes of homemade publications, information fromnewspapers and magazines, who's who files, sport records, telop files,and scripts, which are all used in mass communication and publishing;and maps, ledgers of roads and rivers, fingerprint files, residentcards, documents of application, notification, license, authorization,statistical documents, and public documents, which are all used ingovernment offices. Particularly, the write-once type optical recordingmedia of the present invention can be advantageously useful for storingrecords of charts and official documents which should never be falsifiedand deleted, and used as electronic libraries for art galleries,libraries, museums, broadcasting stations, etc.

As a rather specific use, the optical recording media of the presentinvention can be used to edit and proofread compact discs, digital videodiscs, laser discs, MD (a mini disc as an information recording systemusing photomagnetic disc), CDV (a laser disc using compact disc), DAT(an information recording system using magnetic tape), CD-ROM (aread-only memory using compact disc), DVD-ROM (a read-only memory usingdigital video disc), DVD-RAM (a writable and readable memory usingdigital video disc), digital photos, movies, computer graphics,publishing products, broadcasting programs, commercial messages,computer programs, video software, audio software, game software, etc.;and used as external program recording means for large computers and carnavigation systems.

Hereinbefore, the use of the light absorbents of the present inventionin the field of optical recording media has been mainly limited tohigh-density optical recording media which use a laser beam with awavelength of 450 nm or less as a writing light. However, in the fieldof optical recording media, the light absorbents of the presentinvention can be also advantageously used as materials for changing orregulating the optical absorption rate or the optical reflection rate inthe existing optical recording media such as CD-Rs, DVD-Rs, and otherhigh-density optical recording media by using in combination, forexample, with one or more other organic dye compounds which aresensitive to a laser beam with a wavelength around 635-650 nm or 775-795nm. When applied to organic-ablation type optical recording media usinga laser beam with a wavelength of 450 nm or less as a writing light, thestyryl dyes of the present invention can be used not to directly formpits on substrates but to indirectly form pits in such a manner that theexcitation energy of a laser beam with a wavelength of 450 nm or less isallowed to transfer to the aforesaid organic dye compounds via thestyryl dyes by using the styryl dyes along with one or more otherorganic dye compounds which are sensitive to a laser beam with a longerwavelength, e.g., a laser beam with a wavelength around 635-650 nm or775-795 nm, resulting in a decomposition of the organic dye compounds.The optical recording media as referred to in the present invention meanoptical recording media in general which use the characteristics of thespecific styryl dyes of the present invention that have an absorptionmaxima at a wavelength of 400 nm or less and substantially absorbvisible light with a wavelength around 400 nm in addition to organicthermal-deformed optical recording media, thermal coloration methodusing the chemical reaction of coloring agents and developers using theheat generated when organic dye compounds absorb light, and thetechnique called “moth-eye type technique” which uses the phenomenonthat the above heat smooths the pattern of periodical unevennessprovided on the surface of the substrates.

Since the styryl dyes of the present invention have absorption maxima ata wavelength of 400 nm or less and substantially absorb visible lightwith a wavelength around 400 nm, the light absorbents of the presentinvention containing the styryl dyes can be advantageously useful in theaforesaid optical recording media and also used as materials forpolymerizing polymerizable compounds by exposure to visible light,sensitizing solar batteries, light absorptive materials for lithography,materials for laser active substances in dye lasers which oscillate inthe blue or violet region, and for dying clothes in combination with oneor more other organic dye compounds which substantially absorb visiblelight. If necessary, in combination with one or more other lightabsorbents capable of absorbing light in the ultraviolet, visible and/orinfrared regions, the light absorbents can be used in clothes in generaland others including building/bedding/decorating products such asdrapes, lace, casements, prints, casement cloth, roll screens, shutters,shop curtains, blankets, thick bedquilts including comforters,peripheral materials for the thick bedquilt, cover for the thickbedquilt, cotton for the thick bedquilts, bed sheets, cushions, pillows,pillow covers, cushions, mats, carpets, sleeping bags, tents, interiorfinish for cars, and window glasses including car window glass; sanitaryand health goods such as paper diapers, diaper-covers, eyeglasses,monocles, and lorgnettes; internal base sheets, linings, and materialsfor shoes; wrappers; materials for umbrellas; parasols; stuffed toys;lighting devices; filters, panels and screens for information displayingdevices such as televisions and personal computers which use cathode-raytubes, liquid crystal displays, electroluminescent displays, and plasmadisplays; sunglasses; sunroofs; sun visors; pet bottles; refrigerators;vinyl houses; lawns; optical fibers; prepaid cards; and windows of ovensincluding electric ovens. When used as wrapping materials, injectionmaterials, and vessels for the above products, the light absorbents ofthe present invention prevent living bodies and products from problemsand discomforts induced by environmental lights such as natural- andartificial-lights or even minimize the above them. Furthermore, they canadvantageously regulate the color, tint, and appearance and control thelight reflected by or passed through the products to a desirable colorbalance.

The following examples describe the preferred embodiments of the presentinvention:

EXAMPLE 1 Styryl Dye

Twenty milliliters (ml) of acetic anhydride and 0.6 ml of triethylaminewere placed in a reaction vessel, and mixed with 4 g of2,3,4-trimethylthiazolium=iodide and 2 g of 4-cyanobenzaldehyde. Theresulting mixture was reacted at 80° C. for one hour under stirringconditions, and then was cooled down. The crystals formed werecollected, washed with ethanol, dissolved in a solution of methanol andchloroform under heating, and then filtered. The obtained filtrate wasdistilled to remove chloroform and cooled down to obtain 1.1 g of ayellow crystal of the styryl dye represented by Chemical Formula 9. Whenmeasured in a conventional manner, the melting point of the crystal was261-263° C.

The styryl dye of this Example with remarkable optical properties hasvarious uses in many fields including those of optical recording mediaas a light absorbent.

EXAMPLE 2 Styryl Dye

Forty milliliters of ethanol and 2 ml of triethylamine were placed in areaction vessel, and mixed with 6 g of1,2,3,3-tetramethyl-3H-indolenium=tosylate and 3 g of3-nitrobenzaldehyde. The resulting mixture was reacted at 80° C. for onehour under stirring conditions, and then was cooled down. The crystalsformed were collected, dissolved in a solution of methanol andchloroform under heating conditions, and then filtered. The obtainedfiltrate was distilled to remove chloroform and cooled to obtain 3.4 gof an orangish yellow crystal of the styryl dye represented by ChemicalFormula 40. When measured in a conventional manner, the melting point ofthe crystal was 233° C.

The styryl dye of this Example with remarkable optical properties hasvarious uses in many fields including those of optical recording mediaas a light absorbent.

EXAMPLE 3 Styryl Dye

Twenty milliliters of ethanol and a very small amount of piperidine wereplaced in a reaction vessel, and mixed with 5 g of1,2-dimethylquinolium=iodide and 2.2 g of 2-formylpyridine. Theresulting mixture was reacted at 80° C. for 20 min under stirringconditions, and then was cooled down. The crystals formed were collectedand recrystallized in ethanol to obtain 1.3 g of an orangish yellowcrystal of the styryl dye represented by Chemical Formula 34. Whenmeasured in a conventional manner, the melting point of the crystal was199-200° C.

The styryl dye of this Example with remarkable optical properties hasvarious uses in many fields including those of optical recording mediaas a light absorbent.

EXAMPLE 4 Styryl Dye

Ten milliliters of dimethylformamide and 1 ml of iodomethyl were placedin a reaction vessel, and mixed with 1 g of the styryl dye obtained inExample 3. The resulting mixture was reacted at 100° C. for one hourunder stirring conditions, and then was cooled. The crystals formed werecollected and recrystallized in ethanol to obtain 0.8 g of an orangishred crystal of the styryl dye represented by Chemical Formula 36. Whenmeasured in a conventional manner, the melting point of the crystal was222-223° C.

EXAMPLE 5 Styryl Dye

Twelve milliliters of ethanol and 0.24 ml of piperidine were placed in areaction vessel, and mixed with 3 g of1,3-diethyl-2-methyl-5,6-dichlorobenzimidazolium tosylate and 1.1 g of4-nitrobenzaldehyde. The resulting mixture was reacted at 80 CC for onehour under stirring conditions, and then was cooled. The crystals formedwere collected, dissolved in a solution of methanol and water underheating conditions, and then filtered. The obtained filtrate wasdistilled to concentrate the solution to half volume and cooled toobtain 1.7 g of a yellow crystal of the styryl dye represented byChemical Formula 23. When measured in a conventional manner, the meltingpoint of the crystal was 287-290° C.

The styryl dye of this Example with remarkable optical properties hasvarious uses in many fields including those of optical recording mediaas a light absorbent.

Although the production conditions and yields are varied in some degreesdepending on the structures of the styryl dyes of the present invention,all the styryl dyes of the present invention including the compoundsrepresented by Chemical Formulae 1 to 60 can be produced in asatisfactory yield by the methods in Examples 1 to 5 or in accordancetherewith.

EXAMPLE 6 Optical Property of Styryl Dye EXAMPLE 6-1 Light AbsorptionCharacteristics of Styryl Dye

The styryl dyes of the present invention represented by ChemicalFormulae 8, 9, 19, 23, 34, 36, 38, 40, and 44 were measured for visibleabsorption spectra when dissolved in methanol and formed into thinlayers over glasses. In parallel, the conventional related compoundrepresented by Chemical Formula 61 was measured for visible absorptionspectrum when formed in a solution and in a thin layer similarly asabove. The results were tabulated in Table 1 and FIGS. 1 to 3 showvisible absorption spectra of the styryl dye of the present inventionrepresented by Chemical Formulae 8, 36, and 61 when formed in a solutionand in a thin layer, respectively. TABLE 1 Chemical Formula 61:

Maximum absorption(nm) Styryl dye Solution Thin layer Remarks ChemicalFormula 8 354 354 Present invention Chemical Formula 9 350 368 Presentinvention Chemical Formula 19 359 366 Present invention Chemical Formula23 334 346 Present invention Chemical Formula 34 364 376 Presentinvention Chemical Formula 36 346 357 Present invention Chemical Formula38 375 430 Present invention Chemical Formula 40 371 383 Presentinvention Chemical Formula 44 372 405 Present invention Chemical Formula61 550 542, 574 Control

As shown in the visible absorption spectra of FIG. 3, the conventionalrelated compound represented by Chemical Formula 61 has absorptionmaxima at a wavelength longer than 400 nm when formed in a solution andin a thin layer. As shown in the results of FIGS. 1 and 2 and Table 1,most of the styryl dyes of the present invention have absorption maximaat a wavelength of 400 nm or less when formed in a solution and in athin layer, and the absorption ends to the side of longer wavelengtharea extended to around 450 nm when formed in a thin layer. Theseresults showed that the styryl dyes of the present invention weredifferent from conventional related compounds and that they weresensitive to a laser beam with a wavelength of 450 nm or less,particularly, a laser beam with a wavelength around 350-450 nm, andsubstantially absorb such a laser beam.

EXAMPLE 6-2 Light-Resistance Improvement of Styryl Dye

Fifteen milligrams (mg) of either of the styryl dyes of the presentinvention represented by Chemical Formulae 9, 19, 23, 34, 36, 38, 40,and 44 was added to three milliliters (ml) of TFP. To the mixture wasadded 2 mg of nitrosodiphenylamine represented by Chemical Formula 62which is used in conventional optical recording media as alight-resistant improver, followed by 5 min ultrasonic energization atambient temperature to dissolve the contents in the solvent. Thereafter,in a conventional manner, a prescribed amount of the resulting solutionwas dropped on either surface of a polished glass substrate, 5 cm×5 cm,while the glass substrate was rotated at a rotation rate of 1,200 rpmfor one minute to uniformly coat the solution thereupon, andsequentially blown with hot air and cold air to form a thin layer on theglass substrate.Chemical Formula 62:

The resulting glass substrate coated with either of the styryl dyes wasmeasured for transmittance (T₀) at a wavelength of 400 nm, and then setto the position seven cm away from a 500 W xenon lamp and exposed to thelight of the lamp for 25 min while sending cold air to the substrate.Immediately after that, the resulting substrate was remeasured fortransmittance (T) at a wavelength of 400 nm, and the transmittance of Tand T₀ for each styryl dye was substituted for the Equation 1 tocalculate the residual percentage (%) of the styryl dye. In parallel,control systems with no light-resistant improver for each styryl dyewere provided. $\begin{matrix}{\text{Equation~~1:}{{{Residual}\quad{percentage}\quad{of}\quad{styryl}\quad{{dye}(\%)}} = {\frac{100 - T}{100 - T_{0}} \times 100}}} & \quad\end{matrix}$ TABLE 2 Residual percentage of styryl dye (%) Withlight-resistant With no light-resistant Styryl dye improver improverChemical Formula 9 91.1 44.8 Chemical Formula 19 76.0 45.9 ChemicalFormula 23 96.6 45.6 Chemical Formula 34 90.0 86.1 Chemical Formula 3699.9 99.0 Chemical Formula 38 93.4 30.0 Chemical Formula 40 97.6 96.0Chemical Formula 44 87.1 61.0

As shown in the results of Table 2, in the system with nolight-resistant improvers, maximum 70% of the styryl dyes had changedwith only 25 min exposure of light to be incapable of exerting theirinherent light absorbent properties. When used in combination with thenitroso compound represented by Chemical Formula 62, over 76% of thestyryl dyes still remained intact without being changed by the exposure.These results indicate that light-resistant improvers are useful tosuppress undesirable changes of the styryl dyes of the present inventionby exposure to natural and artificial light.

EXAMPLE 7 Optical Recording Medium

Either of the styryl dyes of the present invention represented byChemical Formulae 8, 9, 19, 23, 34, 36, 38, 40, and 44 as a lightabsorbent was admixed with TFP to give a concentration of 3.0% (w/w),and the mixture was further added the nitroso compound represented byChemical Formula 62 to give a concentration of 0.35% (w/w), heated for awhile, followed by ultrasonically dissolving the contents. The resultingsolution was in a conventional manner filtered through a membrane,coated in a rotatory manner over one side of an acrylic disc substrate,12 cm in diameter, to which had been transferred concaves for expressingsynchronizing signals and addresses of tracks and sectors by aninjection molding, to give a thickness of 200 nm. Thereafter, thesubstrate was spattered with silver to form a reflection layer, 100 nmin thickness, to be closely attached on the surface of the recordinglayer by vaporization, and the reflection layer was homogeneously coatedin a rotatory manner with “DAICURE CLEAR SD1700”, a known ultravioletray hardening resin commercialized by Dainippon Ink and Chemicals, Inc.,Tokyo, Japan, and irradiated to form a protection layer to be closelyattached on the surface of the reflection layer, followed by obtainingnine types of optical recording media.

All of the optical recording media of this Example can be used forwriting large amounts of information in the form of documents, images,and sound at a relatively-high density by using a laser element with anoscillation wavelength of 450 nm or less.

As described above, the present invention was made based on the creationof novel styryl dyes and the findings of their industrially usablecharacteristics. Since the styryl dyes of the present invention haveabsorption maxima at a wavelength of 400 nm or less and substantiallyabsorb visible light with a wavelength around 400 nm, they havediversified uses in the fields of optical recording media, photochemicalpolymerization, dye laser, solar batteries, lithography, dyeing, etc.,which need organic compounds with such properties. Particularly, amongthe styryl dyes, they, being sensitive to a laser beam with a wavelengthof 450 nm or less, are advantageously useful as a material for arecording layer of high-density optical recording media such as DVD-Rs.

As compared with the conventional DVD-Rs which use polymethine dyes as alight absorbent and write information by using a laser beam with awavelength of 635 nm or 650 nm, the optical recording media of thepresent invention, which include the styryl dyes of the presentinvention and use a laser beam with a wavelength of 450 nm or less as awriting light, can form minute pits at a relatively narrower track pitchand a relatively high density. Accordingly, when used the opticalrecording media of the present invention, they can record a vast amountof information of characters, images, and sound at a relatively-highdensity, resulting in greatly lowering the cost of recording informationper bit and recording animations for a long time, which need muchrecording volume, of course standing picture as a merit.

The useful styryl dyes can be easily prepared in a desirable amount bythe process of the present invention which comprises a step of reactinga quaternary ammonium salt of nitrogen heterocyclic compound having anactive methyl- or active methylene-group with an aldehyde compound.

The present invention having such outstanding effects and functions is asignificant invention that will greatly contribute to this art.

1. A styryl dye represented by Formula 1: Formula 1:

wherein in Formula 1, φ₁ represents a heterocycle represented by any oneof Formulae 2 to 8; φ₂ represents an optionally substituted aromaticring or heterocycle; R₁ represents a hydrogen atom, an aliphatichydrocarbon group, ether group, acyl group, halogen, or cyano group, andthe aliphatic hydrocarbon group, ether group, and acyl group may have asubstituent; X⁻ represents a counter ion; and “n” is a number of X⁻ tobalance the electric charge in the styryl dye:

throughout Formulae 2 to 7, A represents an optionally substitutedmonocyclic or polycyclic aromatic ring or heterocycle; when A is notpresent in Formulae 2 to 7, a substituent similar to A is in positionfilled by A; throughout Formulae 2 to 8, R₂ represents an optionallysubstituted aliphatic hydrocarbon group and R₃ represents a hydrogen oran optionally substituted aliphatic hydrocarbon group which is identicalto or different from R₂.
 2. The styryl dye of claim 1, wherein said φ₂is a nitrogen atom containing heterocycle which forms an ammonium salt.3. The styryl dye of claim 1 wherein said counter ion is an organicmetal complex anion with a light-resistant improving ability.
 4. Thestyryl dye of claim 1 which has an absorption maximum at a wavelength of400 nm or less.
 5. The styryl dye of claim 1 which substantially absorbsa visible light with a wavelength of 450 nm or less when formed in athin layer.
 6. A process for producing the styryl dye of claim 1comprising reacting a compound, represented by Formula 9 having φ₁ andR₁ corresponding to Formula 1, with a compound represented by Formula 10having φ₂ corresponding to Formula
 1.


7. The styryl dye of claim 2, wherein said counter ion is an organicmetal complex anion with a light-resistant improving ability.
 8. Thestyryl dye of claim 2 which has an absorption maximum at a wavelength of400 nm or less.
 9. The styryl dye of claim 3 which has an absorptionmaximum at a wavelength of 400 nm or less.
 10. The styryl dye of claim 2which substantially absorbs visible light with a wavelength of 450 nm orless when formed in thin layer.
 11. The styryl dye of claim 3 whichsubstantially absorbs visible light with a wavelength of 450 nm or lesswhen formed in thin layer.
 12. The styryl dye of claim 4 whichsubstantially absorbs visible light with a wavelength of 450 nm or lesswhen formed in thin layers.